| Community Network Services Ltd | Association / organization | 204-206 Berth | Daily Open 24 hours |
| Computer Problems Solved Ltd | Computer consultant | 68 Orchardlea | Mon–Sat 09:00–17:00 |
| Considerate Carnivore | Meat products store | Unit 7 Centre Way | Mon–Sat 08:30–17:00 |
| Convoi Exceptionnel Ltd Abnormal Loads | Transportation escort service | Mitchell Point, Ensign Way | Mon–Fri 07:30–18:00 |
| County Locksmiths | Locksmith | 389B Bitterne Rd | Mon 09:00–17:00 |
| County Tile Warehouse - Tile and Bathroom Showroom | Southampton | Tile shop | Unit 1, Third Ave | Mon–Fri 07:30–16:30 |
| CoverDent | Dental insurance agency | Freemantle Business Centre, 152 Millbrook Rd E | Mon–Fri 09:00–17:00 |
| Creative Kidz Childcare Ltd at Hamble Primary School | After-school programme | Hamble Primary School, Hamble Ln | Wed–Thu 07:30–08:45, 15:00–18:00 |
| Creative Kidz Childcare Ltd at Netley Abbey | After-school programme | Infant and Junior Schools, The Federation of, Westwood Rd | Wed–Thu 07:30–08:45, 15:00–18:00 |
| Creature Comforts & Aquatic Centre | Pet shop | 13-15 Ringwood Rd | Thu 09:00–17:30 |
| Crescent Motorcycles Southampton | Motorbike dealer | Lowford Hill, Portsmouth Rd | Sat 09:00–17:00 |
| Cruise Azure Parking Southampton Port Parking | Valet parking service | Southampton SO15 0JA | Mon 07:00–15:00 |
| CrunchWise Chartered Accountants | Tax preparation service | Southampton SO15 2EP | Thu 08:00–18:00 |
| Cruze Motor Company Ltd | Used truck dealer | Greenaway Ln | Sun 11:00–13:30 |
| Cryers Letting Agents Southampton | Apartment rental agency | 26 London Rd | Mon 09:00–17:30 |
| Curbridge Engineering Ltd | Sheet metal contractor | Unit 17, Solent Industrial Estate, Shamblehurst Ln S | Mon–Thu 07:30–16:30 |
| Curran Dental Engineers Ltd | Engineer | Unit 11, Claylands Park | Mon–Fri 08:00–17:30 |
| CW Plant Hire Generator & Pump Hire | Electric generator shop | 29 Winchester Rd | Mon–Fri 09:00–17:00 |
| D & S Surfacing Contractors | Asphalt contractor | 63 Botany Bay Rd | Thu 09:00–17:00 |
| D P P Ltd | Mechanical contractor | Prospect House, 14 Bartram Rd | Mon–Wed 09:00–17:00 |
| Daedalus Drylining & Plastering | Dry wall contractor | Stanton Buildings, Unit 1 Stanton Rd, Regents Park Rd | Daily Open 24 hours |
| Daly Brickwork Ltd | Bricklayer | Clifford St | Daily 07:00–19:00 |
| Damira Dental | Dentist | 10 Cannon St | Daily 08:00–20:00 |
| Damira Shirley Dental Practice | Dentist | 10-12 Cannon St | Daily 08:00–20:00 |
| David Mellor Family Jewellers | Jeweller | 35 Totton Precinct | Mon–Sat 09:30–17:00 |
| Dearden Motorcycles Ltd | Motorbike dealer | Unit 5, Hardley Industrial Estate | Tue–Sat 08:30–17:30 |
| DEBRA Charity Shop | Charity | 6A Water Ln | Mon–Sat 09:00–17:00 |
| Desty Marine - Yacht Repairs & Refits | Boat maintenance | Hamble Point Marina, School Ln | Mon–Fri 08:30–17:00 |
| Dhaba | Indian restaurant | 59 Lodge Rd | Mon 16:00–21:00 |
| Diego's Rotisserie - Restaurant in Southampton | Portuguese restaurant | 10 Bedford Pl | Mon 12:00–22:00 |